Patent application title: METHOD AND SYSTEM FOR CORRELATING TOMOGRAPHICALLY CONTROLLED INTERVENTIONAL PROCEDURES WITH PATIENT POSITION IN THE RESPIRATORY CYCLE

Abstract:

In a method and an imaging system for implementing a CT-assisted or
MRT-assisted minimally-invasive interventional procedure at an anatomical
location inside the body of a patient, the inspiratory or respiratory
position of the patient within the respiratory cycle of the patient is
continuously detected and a measurement value, identifying a current
position of the patient within the respiratory cycle, is detected at a
point in time that a CT or MRT slice image of the anatomical location is
obtained. This measurement value is stored together with the image data
of the slice image so that the measurement value and the image data can
be retrieved together and displayed together.

Claims:

1. A method for implementing a tomographically-assisted,
minimally-invasive interventional procedure of a patient, comprising the
steps of:continuously detecting successive inspiratory/expiratory
positions of a patient within a respiratory cycle of the patient;at an
image acquisition time, acquiring a tomographic image, selected from the
group consisting of CT images and MRT images, of a slice of the patient
containing an anatomical location to be treated, said image being
comprised of image data;at said image acquisition time, identifying a
measurement value, from among said continuously detected
inspiratory/respiratory positions within the respiratory cycle of the
patient, that represents an inspiratory/respiratory position of the
patient at said image acquisition time;electronically storing said
measurement value and said image data in an associated relationship;
andretrieving the associated measurement value and image data from
storage and displaying said image data together with said measurement
value.

2. A method as claimed in claim 1 comprising:instructing the patient to
perform a breath hold and, during said breath hold, measuring a threshold
value of pulmonary pressure in the lungs of the patient;continuously
detecting said inspiratory/respiratory position of the patient by
continuously detecting said pulmonary pressure; andautomatically
initiating acquisition of said tomographic slice image, at said image
acquisition time, when the continuously detected pulmonary pressure is
within a tolerance range bounded by two predetermined boundaries of
respectively different magnitudes around said threshold.

3. A method as claimed in claim 2 comprising automatically ending said
image acquisition when said pulmonary pressure assumes a value outside of
said tolerance range.

4. A method as claimed in claim 3 wherein the beginning and ending of said
image acquisition define a scan and wherein said two predetermined
thresholds of different magnitudes comprise a lower threshold and an
upper threshold, and comprising continuously detecting values of said
pulmonary pressure when said pulmonary pressure is below said lower
threshold and when said pulmonary pressure is above said upper threshold,
and identifying a plurality of values representing inspiratory/expiratory
breathing volume of the patient from said plurality of values of said
pulmonary pressure, and generating a computerized report file of said
scan that includes a representation of said breathing volume of the
patient with respect to time.

5. A method as claimed in claim 4 comprising generating an analog
indicator signal, selected from the group consisting of optical signals,
acoustic signals, and haptic signals, having a signal amplitude
proportional to the detected pulmonary pressure when said pulmonary
pressure falls below said lower threshold or exceeds said upper
threshold.

6. A method as claimed in claim 5 comprising generating said indicator
signal as an optical signal represented by a row of light-emitting
diodes, comprising a central light-emitting diode that is located in a
middle of said row, and representing said magnitude of said indicator
signal by illumination of a corresponding number of said light-emitting
diodes in said row, and causing said central light emitting diode to
change emission color when said pulmonary pressure falls below said lower
threshold or when said pulmonary pressure exceeds said upper threshold.

7. A method as claimed in claim 4 comprising, after said scan, identifying
an extreme value of said pulmonary pressure, selected from the group
consisting of a maximum value and a minimum value, and including an
identification of said extreme value in said computerized report file
and, if said extreme value is within said tolerance range, automatically
adapting one of said lower threshold and said upper threshold to said
extreme value for automatically initiating or ending a next scan of the
patient during said interventional procedure.

8. A method as claimed in claim 7 comprising conducting a plurality of
scans of the patient during said interventional procedure and generating
said computerized report file for each of said scans, and identifying an
average value of said extreme value for said plurality of said scans and
adapting said at least one of said minimum value and said maximum value,
for said next scan, to said average value of said extreme value.

9. A method as claimed in claim 4 comprising, after said scan,
automatically generating a calibration signal representing a desired
value of said pulmonary pressure between a, maximum value of said
pulmonary pressure and a minimum value of said pulmonary pressure
detected during said scan, and including said calibration signal in said
computerized report file for said scan and, for a next scan during said
interventional procedure, automatically adapting at least one of said
lower threshold or said upper threshold relative to said calibration
signal.

10. A method as claimed in claim 9 comprising implementing a plurality of
scans during said interventional procedure and generating said
computerized report file for each of said scans, and generating an
average value of said calibration signal for said plurality of said scans
and, for said next scan, automatically adapting said lower threshold and
said upper threshold to said average value of said calibration signal.

11. An image acquisition system for implementing a
tomographically-assisted, minimally-invasive interventional procedure of
a patient, comprising:a detector configured to continuously detect
successive inspiratory/expiratory positions of a patient within a
respiratory cycle of the patient;a tomographic scammer configured to
acquire, at an image acquisition time, a tomographic image, selected from
the group consisting of CT images and MRT images, of a slice of the
patient containing an anatomical location to be treated, said image being
comprised of image data;a measurement and display system configured to
identify, at said image acquisition time, identifying a measurement
value, from among said continuously detected inspiratory/respiratory
positions within the respiratory cycle of the patient, that represents an
inspiratory/respiratory position of the patient at said image acquisition
time, and to electronically store said measurement value and said image
data in an associated relationship, and to retrieve the associated
measurement value and image data from storage and to display said image
data together with said measurement value.

12. An image acquisition system as claimed in claim 11 comprising:wherein
said measurement and display system, during a breath hold by the patient
is configured to measure a threshold value of pulmonary pressure in the
lungs of the patient;said detector comprising a pulmonary pressure
detector; anda control unit in communication with said measurement and
display system, configured to automatically initiate acquisition of said
tomographic slice image, at said image acquisition time, when the
continuously detected pulmonary pressure is within a tolerance range
bounded by two predetermined boundaries of respectively different
magnitudes around said threshold.

13. An image acquisition system as claimed in claim 12 wherein said
control unit is configured to automatically end said image acquisition
when said pulmonary pressure assumes a value outside of said tolerance
range.

14. An image acquisition system as claimed in claim 13 wherein the
beginning and ending of said image acquisition define a scan and wherein
said two predetermined thresholds of different magnitudes comprise a
lower threshold and an upper threshold, and wherein said detector is
configured to continuously detect values of said pulmonary pressure when
said pulmonary pressure is below said lower threshold and when said
pulmonary pressure is above said upper threshold, and wherein said
measurement and display system is configured to identify a plurality of
values representing inspiratory/expiratory breathing volume of the
patient from said plurality of values of said pulmonary pressure, and to
generate a computerized report file of said scan that includes a
representation of said breathing volume of the patient with respect to
time.

15. An image acquisition system as claimed in claim 14 wherein said
measurement and display system is configured to generate an analog
indicator signal, selected from the group consisting of optical signals,
acoustic signals, and haptic signals, having a signal amplitude
proportional to the detected pulmonary pressure when said pulmonary
pressure falls below said lower threshold or exceeds said upper
threshold.

16. An image acquisition system as claimed in claim 15 wherein said
measurement and display system is configured to generate said indicator
signal as an optical signal represented by a row of light-emitting
diodes, comprising a central light-emitting diode that is located in a
middle of said row, and to represent said magnitude of said indicator
signal by illumination of a corresponding number of said light-emitting
diodes in said row, and to cause said central light emitting diode to
change emission color when said pulmonary pressure falls below said lower
threshold or when said pulmonary pressure exceeds said upper threshold.

17. An image acquisition system as claimed in claim 14 wherein said
measurement and display system is configured to identify, after said
scan, an extreme value of said pulmonary pressure, selected from the
group consisting of a maximum value and a minimum value, and including an
identification of said extreme value in said computerized report file
and, if said extreme value is within said tolerance range, to
automatically adapt one of said lower threshold and said upper threshold
to said extreme value for supply to said control unit for automatically
initiating or ending a next scan of the patient during said
interventional procedure.

18. An image acquisition system as claimed in claim 17 wherein said
control unit is configured to conduct a plurality of scans of the patient
during said interventional procedure and wherein said measurement and
display unit is configured to generate said computerized report file for
each of said scans, and to identify an average value of said extreme
value for said plurality of said scans and to adapt said at least one of
said minimum value and said maximum value, for said next scan, to said
average value of said extreme value.

19. An image acquisition system as claimed in claim 14 wherein said
measurement and display system is configured, after said scan, to
automatically generate a calibration signal representing a desired value
of said pulmonary pressure between a maximum value of said pulmonary
pressure and a minimum value of said pulmonary pressure detected during
said scan, and to include said calibration signal in said computerized
report file for said scan and, for a next scan during said interventional
procedure, to automatically adapt at least one of said lower threshold or
said upper threshold relative to said calibration signal.

20. An image acquisition system as claimed in claim 19 wherein said
control unit is configured to implement a plurality of scans during said
interventional procedure and generate said computerized report file for
each of said scans, and to generate an average value of said calibration
signal for said plurality of said scans and, for said next scan, to
automatically adapt said lower threshold and said upper threshold to said
average value of said calibration signal.

21. A computer-readable medium encoded with programming instructions for
operating an imagery system and a detector to implement a
tomographically-assisted, minimally-invasive interventional procedure of
a patient, said medium being loadable into a control arrangement for said
imaging system and detector and said programming instructions
causing:said detector to continuously detect successive
inspiratory/expiratory positions of a patient within a respiratory cycle
of the patient;said imaging system to acquire at an image acquisition
time, a tomographic image, selected from the group consisting of CT
images and MRT images, of a slice of the patient containing an anatomical
location to be treated, said image being comprised of image data; andsaid
control arrangement to identify, at said image acquisition time, a
measurement value, from among said continuously detected
inspiratory/respiratory positions within the respiratory cycle of the
patient, that represents an inspiratory/respiratory position of the
patient at said image acquisition time, and to electronically store said
measurement value and said image data in an associated relationship, and
to retrieve the associated measurement value and image data from storage
and to display said image data together with said measurement value.

Description:

BACKGROUND OF THE INVENTION

[0001]1. Field of the Invention

[0002]The present invention concerns an image acquisition system usable in
the field of diagnostic and interventional radiology as well as a method
for implementation of CT-controlled or MRT-controlled minimally-invasive
interventional procedures for internal organs, tissue regions, lesions
(for example in the region of lungs and liver) or pathological structures
inside the body of a patient (for example at tumor sources, metastases,
hematomas, abscesses etc.) in correlation with the patient's inspiratory
or expiratory position (phase) within the respiratory cycle, which serves
to improve the precision and safety of the minimally-invasive procedures,
in particular in the field of diagnosis tissue sample extraction (biopsy)
implemented under CT-assisted or MRT-assisted imaging monitoring after
local anesthesia as well as in tumor and pain therapy.

[0003]2. Description of the Prior Art

[0004]Today the histomorphological and cytomorphological examination of
tissue samples is an indispensable method for clinical assessment of a
number of benign and malignant clinical situations. Today histological
(tissue structure) examination can be applied to all organs due to
perfected extraction and examination methods. Hematological diagnostics
from bone marrow, spleen and lymph nodes as well as tumor diagnostics
from mammary glands, lungs, liver, thyroid and prostate are of particular
importance. Cerebrospinal fluid (liquor cerebrospinalis) and effusions
from the pleural cavity (cavitas pleuralis) or the abdominal cavity have
been able to be obtained by centesis and cyto-diagnostically examined for
a long time. An important addition to this is centesis (puncture)
cytology that is used for the grading of malignant tumors, cancer
precautions and early cancer detection. Today there is thus practically
no specific therapy without preceding histological or cytological
confirmation of the diagnosis.

[0005]The rapid development of imaging methods, in particular sonography,
as well as computed tomography in the 1970s, allowed an improved
localization of pathological findings since an exact and overlap-free
representation of soft tissue structures could be achieved. During the
same time period, great advances were made in the precision of the
interpretation of tissue fragments. For histological clarity or in the
case of an unclear finding, centesis implemented under
computer-tomographical or sonographical monitoring represents a suitable
technique for clarification. Today percutaneous punch biopsy and needle
puncture procedures have developed into an important instrument in
diagnostics and therapy monitoring.

[0006]Today locally occurring tumors or metastases (for example in the
region of the liver or lung) can be safely diagnosed through a
percutaneous, minimally-invasive procedure by means of fine needle biopsy
and can be treated without implementation of surgery. For this purpose,
special probes or hollow needles (puncture needles) are inserted through
the skin into the tumor to be treated. Depending on the method, the tumor
can then be therapeutically treated locally by action of cold or heat, or
chemically. The selection of the respective interventional method is made
on the basis of the size, position and condition of the tumor in
question. The destroyed tumor is broken down by the body after the
procedure and the treated tissue scars over. In order to be able to
implement the placement of the probe or needles as precisely as possible,
the procedures (for example radio-frequency ablation, cryotherapy or
alcohol ablation) are typically implemented under slice image monitoring.
Both magnetic resonance tomography and computed tomography are used for
this purpose. All of these methods are normally conducted under local
anesthesia and allow an implementation of the respective procedure with
millimeter precision. Depending on the size and position of the tumors it
may be necessary to use a number of probes simultaneously and to repeat
the procedures.

[0007]In cryotherapy the tissue destruction ensues by a rapid cooling of
the tumor tissue to temperatures between -50° C. and -150°
C. with the use of a coolant (for example argon gas) inserted into a
probe. This leads to an irreversible destruction of the cells as well as
a sealing of the smallest arteries and veins. A characteristic of the
cryo-treatment is the almost complete absence of pain since the cold
inherently has an analgesic effect, and an additional pain therapy (local
anesthesia) is not required. The extent of the frozen tumor can be
depicted very well by magnetic resonance tomography. A high precision of
the tissue destruction during the treatment is thus possible.

[0008]Radio-frequency therapy (RF ablation) is a hyperthermic ablation
method for cancer therapy that destroys a primary tumor or a metastasis
via heat. The heat is achieved by a flexible probe that is inserted into
the tumor source under ultrasound or CT monitoring. A radio-frequency
alternating current that leads (via the probe) to a temperature increase
in the tissue to 90° C. to 120° C. is generated via a
radio-frequency generator. The tumor is thereby necrotized in situ. The
advantage of the RF ablation lies in the small diameter of the probes
used (approximately 2 mm) and the achievable lesion size (up to 5 cm
without probe displacement). The monitoring of the tumor destruction
ensues depending on the employed apparatus, for example via a direct or
indirect temperature measurement or a determination of the conductivity
of the tissue or its impedance during the procedure. This occurs through
the probe itself; additional probes are not required. After a successful
tumor treatment the puncture path is coagulated during the probe removal,
i.e. is sealed by the effect of heat. Spreading of the tumor cells thus
does not occur. Since the heat treatment of metastases or tumors can be
painful depending on the position and organ, the procedure occurs under
liberal administration of analgesics or anesthesia. The duration of the
procedure is approximately one hour depending on the size and number of
the treated metastases.

[0009]In alcohol ablation, a tumor to be treated is obliterated with the
use of high concentration of alcohol solution. The tumor is thereby
punctured with one or more fine puncture needles under CT or MRT
monitoring with local anesthesia. Given correct needle position the
injection occurs with 95% alcohol mixed with some anesthesia agent in the
center of the tumor. Depending on the tissue condition, tumor type and
localization, the quantity of alcohol varies between 5 ml and 50 ml. A
repeated treatment can be required in the case of larger tumors. The
effect of the alcohol is based on a dehydration of the cells, denaturing
of protein and thrombosis of the smallest vessels. The consequence is a
coagulation necrosis that is subsequently broken down by the body and
scarred over. This technique has proved to be particularly effective for
treating hepatocellular carcinoma (HCC) since this type of carcinoma
exhibits a tumor cyst and the alcohol homogeneously distributes within
the tumor. The distribution of the alcohol can be unpredictable in the
case of liver metastases, so in these cases the success of this treatment
is not exactly predictable. The minimal controllability of the alcohol
distribution for liver metastases (with the exception of HCC) as well as
the pain stress given positions of the tumors near the cyst are
disadvantages. The indication for alcohol ablation thus very much depends
on the condition, consistency and localization of the tumor in question.

[0010]Transarterial chemo-embolization (TACE) is a conservative but
effective therapy method for treatment of hepatocellular carcinoma. An
obliteration of the tumor tissue by targeted administration of a
chemotherapy compound (epirubicin) by a precise injection is enabled
through an access from the groin with a flexible, thin catheter. A very
high concentration of the medicine is achieved in the tumor via this
method while the exposure of the rest of the body regions due to the
chemotherapy is relatively slight.

[0011]CT-controlled puncture of tissue or organs with subsequent
cytological and histological (fine-tissue) examination of the puncture
specimen, CT-controlled drainage treatment as well as CT-controlled
neurolysis and facet block count are among the further applications of
computed tomography in the field of diagnostics and minimally-invasive
therapy.

[0012]CT-controlled diagnostic puncture is a conservative method in which,
after disinfection of the skin and local anesthesia, a hollow needle is
inserted under CT-based fluoroscopy monitoring into a tissue region or an
organ of a patient to be examined, whereupon tissue samples (biopsies)
are extracted, for example in order to be able to reliably classify the
nature of a localized tumor as benign or malignant. A local anesthesia is
normally sufficient. The extracted tissue samples are subsequently sent
to a medical laboratory for histological exam. This diagnosis method is
in particular applies when unclear expansive lesions are to be
differentiated in the region of the thorax and the abdomen (for example
in the lungs, kidneys, lymph nodes or liver).

[0013]A CT-controlled drainage is a minimally-invasive method in which
detected abscesses (pus accumulations) and infected hematomas inside the
body of a patient are drained out through an interventional procedure via
a percutaneously inserted drainage catheter under CT-controlled imaging
monitoring. After a suspicion diagnosis posed using CT slice exposures, a
CT-controlled puncture is initially implemented to ensure the diagnosis
and the microbiological germ and resistance determination. The
percutaneous drainage then ensues via the same penetration point. The
procedure is analogous to the CT-controlled tissue sample extraction,
with the difference that now a drainage tube remains that allows a
drainage and irrigation of the pathological fluid accumulation.

[0014]In a CT-controlled neurolysis and facet block, specific nerve
bundles are switched off via targeted injection of suitable substances
(alcohol and anesthesia) under CT monitoring for the purpose of pain
therapy (for example in the case of certain spinal column illnesses) or
to improve the peripheral arterial blood circulation. The interventional
procedure is advantageously implemented in the prone position. If a prone
position is not possible with a particular patient, a position must be
selected that can be maintained for the entire duration of the procedure
and that simultaneously allows the physician an easy access to the point
of the body to be treated. As is the case before any procedure, possible
risks of the treatment and the measurement of his blood values are
explained to the patient. In a facet block procedure, pain treatment of
the small zygoapophyseal joints (facets) in the spinal column ensues by
injection of a locally effective anesthetic and triamcinolone (a
relatively long-acting cortisone preparation) into the facet joints.

[0015]In a periradicular therapy (PRT), which (in the case of a herniated
intervertabral disc) is in particular indicated as a pain therapy method
for treatment of the nerve root exiting from the spinal canal of the
spinal column between the lumbar vertebrae, a fine puncture needle is fed
into the immediate proximity of the existing spinal cord nerves under
local anesthesia and computer tomography imaging. There medicine
containing a corticosteroid is then injected which should cause a
decrease of the local tissue swelling and thus a "release" of clamped
nerves.

[0016]In principle there are two possibilities for CT-assisted visual
monitoring of a minimally-invasive intervention. The treating physician
can generate an individual CT slice exposure (for example via actuation
of a foot switch) without table feed in order to acquire a current
projection representation of an organ or tissue region to be treated as
well as image information with regard to the position of an inserted
puncture needle, a probe or another medical instrument typically used for
implementation of an interventional procedure. After generation of the
exposure, it can occur that the considered CT slice plane shifts as a
result of a body movement of the patient or due to inhalation or
exhalation. The radiologist implementing the interventional procedure
then has the possibility to monitor the position of the needle tip with
the use of the aforementioned CT slice exposure in order to be able to
alter the needle position without real-time image monitoring. The
physician thus does not see the penetration and advancement of the
puncture needle on a screen terminal in real time, but only when the
physician generates the next CT slice exposure by re-actuation of a foot
switch. In contrast to this, the second possibility is to generate images
in a continuous sequence in CT fluoroscopy. The possibility of a
real-time monitoring of therapeutic or diagnostic procedures thereby
exists. Medical instruments inserted into a penetration point can thereby
be continuously tracked on the monitor. The radiation exposure of both
the radiologist and the patient, however, is problematically distinctly
increased relative to the previously illustrated individual image
acquisition.

SUMMARY OF THE INVENTION

[0017]Starting from the aforementioned prior art, an object of the present
invention is to increase the precision and safety of CT-controlled or
MRT-controlled, minimally-invasive interventional procedures.

[0018]This object is achieved in accordance with the present invention by
a method usable (in particular in the field of diagnostic and
interventional radiology) for implementation of a CT-controlled or
MRT-controlled, minimally-invasive intervention at internal organs,
tissue regions, lesions (for example in the area of spinal cord nerve
roots) or pathological structures inside the body of a patient (for
example at tumor sources, metastases, hematomas, abscesses etc.). In the
inventive method, the position within the respiratory cycle in an
inspiration and/or expiration state of the patient is continuously
detected; and a respective measurement value detected at the point in
time of the acquisition of a CT or MRT slice image of the organ, tissue
regions, lesions or pathological structures to be treated. The
measurement value reflects the current position of the patient within the
respiratory cycle, and is stored together with the image data of this CT
or MRT slice image such that they can be retrieved, and the measurement
value is displayed. In addition to the acquired CT or MRT slice image,
which enables a direct comparison of the current anatomical state of this
patient with the acquired state, a radiologist implementing the
interventional procedure has at hand a further decision criterion in
order to assess or monitor whether the tip of a puncture needle used to
implement the minimally-invasive procedure is at the correct point that
was suitably established before implementation of the procedure. This is
always the case only when the currently detected and indicated position
of the patient within the respiratory cycle coincides with the position
within the respiratory cycle stored together with the acquired CT or MRT
slice image.

[0019]According to the invention, a CT or MRT scan is automatically
initiated when the inspiratory or expiratory pulmonary pressure that is
developed by the lungs of the patient (and therewith the breathing volume
in the inspiration or expiration state of the patient) moves around a
predeterminable threshold within a tolerance range bounded by two
predeterminable thresholds of different magnitudes after issuing a
breath-hold command. According to the invention, the CT or, respectively,
MRT scan is automatically ended as soon as the inspiratory or expiratory
pulmonary pressure assumes values outside of the tolerance range bounded
by the two predeterminable thresholds.

[0020]The values of the inspiratory or expiratory pulmonary pressure are
continuously detected as long as the lower of the two thresholds is not
exceeded or the upper of the two thresholds is exceeded. The associated
values of the inspiratory or expiratory breathing volume and/or the
points in time of these thresholds being exceeded or not are protocolled
in a time-discrete and value-discrete manner in a report file at the end
of each CT or MRT scan process.

[0021]According to the invention, the signal amplitude of an analog
measurement signal proportional to the detected inspiratory or expiratory
pulmonary pressure can be indicated by an optical, acoustic and/or haptic
signal upon an under-run of the lower of the two thresholds or upon an
over-run of the upper of the two thresholds. According to the invention,
the signal amplitude of the analog measurement signal proportional to the
detected inspiratory or expiratory pulmonary pressure is indicated, for
example, by illumination of a corresponding number of light-emitting
diodes of at least one light-emitting diode row to the left and right of
a light-emitting diode emitting light of a different color upon under-run
of the lower of the two thresholds or upon over-run of the upper of the
two thresholds. The light-emitting diode that emits light of a different
color is mounted in the middle of this at least one light-emitting diode
row.

[0022]According to the invention, after conclusion of a CT or MRT scan the
two preset thresholds can be respectively, automatically adapted to the
minimal value (detected during this scan process and protocolled in the
aforementioned report file), or to the maximal value (likewise detected
during this scan and protocolled in the report file) of the detected
inspiratory or expiratory pulmonary pressure, insofar as this minimal
value or this maximal value lies within the tolerance range bounded by
the two thresholds.

[0023]Alternatively, after conclusion of a CT or MRT scan, the two preset
thresholds can respectively, automatically be adapted to the minimal
value (determined over all preceding CT or MRT scan processes and
protocolled in the aforementioned report file), or to the maximal value
(likewise determined over all preceding CT or MRT scan processes and
protocolled in the aforementioned report file) of the detected
inspiratory or expiratory pulmonary pressure, insofar as this minimal
value or, respectively, this maximal value lies within the tolerance
range bounded by the two thresholds.

[0024]According to the invention, at the end of each CT or MRT scan, a
calibration signal can be generated with which the predeterminable
desired value of the measured inspiratory or expiratory pulmonary
pressure is automatically established at an intermediate value between
the minimal value (detected during this CT or MRT scan and protocolled in
the report file) and the maximal value (likewise detected during this
scan process and protocolled in the report file) of the inspiratory or
expiratory pulmonary pressure. The intermediate value is thereby selected
such that it lies within the tolerance range bounded by the two
thresholds.

[0025]Alternatively, at the end of each CT or MRT scan process a
calibration signal can be generated with which the predetermined desired
value of the measured inspiratory or expiratory pulmonary pressure is
automatically established at an intermediate value between the minimal
value (determined over all preceding CT or MRT scan processes and
protocolled in the aforementioned report file) and the maximal value
(likewise determined over all preceding CT or, respectively, MRT scan
processes and protocolled in the aforementioned report file) of the
inspiratory or expiratory pulmonary pressure. The intermediate value is
thereby selected such that it lies within the tolerance range bounded by
the two thresholds.

[0026]The object also is achieved in accordance with the present invention
by an image acquisition system for generation of image data that are
required for CT-assisted or MRT-assisted imaging monitoring of a
minimally-invasive intervention at internal organs, tissue regions,
lesions (for example in the region of the spinal cord nerve roots) or
pathological structures inside the body of a patient (for example at
tumor sources, metastases, hematomas, abscesses etc.). The image
acquisition system has a control device that causes a measurement value,
reflecting the current position within the respiratory cycle (the
inspiratory or expiratory state of the patient) at the point in time of
the acquisition of a CT or MRT slice image of the organs, tissue regions,
lesions or pathological structures to be treated, to be stored together
with the image data of this CT or MRT slice image such that it can be
retrieved and displayed with the image.

[0027]According to the invention the control device can be programmed to
automatically initiate a CT or MRT scan process when the inspiratory or
expiratory pulmonary pressure of the patient moves around a
predeterminable desired value within a tolerance range bounded by two
predetermined thresholds of different values after a breath-hold
instruction to the patient, and to automatically end the CT or MRT scan
when the inspiratory or expiratory pulmonary pressure of the patient
assumes values outside the tolerance range bounded by these two
predeterminable thresholds.

[0028]The inventive image acquisition system moreover has a threshold
evaluator formed as a window discriminator and connected with a
measurement signal input of the control device, the threshold evaluator
supplies a binary output signal that (assuming positive logic) only
assumes the value of "logical one" when the detected inspiratory or
expiratory pulmonary pressure of the patient moves within a tolerance
range bounded by the two predeterminable thresholds.

[0029]Using a pneumograph that serves for continuous measurement of the
inspiratory or expiratory pulmonary pressure, changes in the length of an
expandable respiratory belt (wrapped around the upper abdomen or around
the lower chest region of the patient) occurring in the inspiration and
expiration process are detected and translated by a pressure-sensitive,
piezoresistive, capacitive or inductive transducer into an analog
measurement signal that is directly proportional to the detected
inspiratory or expiratory pulmonary pressure.

[0030]Furthermore, the inventive image acquisition system has a
respiration monitoring and display system with at least one display unit
which is used to display the signal amplitude of a measurement signal
proportional to the detected inspiratory or expiratory pulmonary pressure
of the patient via a light signal of the at least one display unit.

[0031]According to the invention, the two thresholds and/or the desired
value can be predetermined by a calibration and control unit integrated
into the inventive image acquisition system.

[0032]The inventive image acquisition system moreover has a radio wave
transmission and reception system with a radio wave transmitter for
wireless transmission of two of the pulmonary pressure thresholds
predetermined by the calibration and control unit to a radio wave
receiver connected with a programmer signal input of the window
discriminator and/or for wireless transmission of a desired pulmonary
pressure value predetermined by the calibration and control unit to a
radio wave receiver connected at the output with the display units of the
respiration monitoring and display system.

[0033]Moreover, a further radio wave transmitter can be provided which
serves to transfer the measurement signal delivered by the
pressure-sensitive piezoresistive, capacitive or inductive transducer of
the pneumograph and proportional to the detected inspiratory or
expiratory pulmonary pressure of the patient wirelessly to a radio wave
receiver of the radio wave transmission and reception system that is
connected with the display units of the respiration monitoring and
display system and/or to a radio wave receiver of this radio wave
transmission and reception system that is connected with the programmer
signal input of the window discriminator.

[0034]The above object also is achieved in accordance with the present
invention by a computer software program product (computer readable
medium encoded with programming instructions) that causes the method
described above to be implemented by a control unit with an associated
screen terminal of an image acquisition system described above.

BRIEF DESCRIPTION OF THE DRAWINGS

[0035]FIG. 1 is a block diagram of an embodiment of an image acquisition
system according to the present invention that is used for monitoring and
display of the pulmonary pressure as well as for CT-assisted imaging
monitoring of a minimally-invasive intervention at internal organs,
tissue regions, lesions or pathological structures of a patient that are
to be punctured.

[0036]FIG. 2 shows a diagram reproducing the characteristic line curve of
the inspiratory or expiratory pulmonary pressure over time during a
respiration period of a patient to be examined, with which diagram it is
illustrated that a CT scan process for imaging monitoring of a
minimally-invasive intervention at internal organs, tissue regions,
lesions or pathological structures of the patient is conventionally
manually initiated by a radiologist, and in fact at a point in time at
which the pulmonary pressure of the patient is at least approximately
constant.

[0037]FIG. 3 shows an additional diagram reproducing the characteristic
line curve of the inspiratory or expiratory pulmonary pressure over time
during a respiration period of a patient to be examined, with which
diagram it is illustrated how the beginning point in time and the
duration of a CT scan to be implemented are determined according to the
present invention.

[0038]FIG. 4 shows a flowchart representing a conventional method for
CT-assisted imaging monitoring of a minimally-invasive procedure
implemented at internal organs, tissue regions, lesions or pathological
structures of a patient after local anesthesia.

[0039]FIG. 5 shows a flowchart representing the inventive method for
CT-assisted imaging monitoring of a minimally-invasive procedure
implemented after local anesthesia at internal organs, tissue regions,
lesions or pathological structures of a patient in correlation with the
patient's position within the respiratory cycle.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040]In the following paragraphs the system components of the inventive
image acquisition system and the steps of the associated inventive method
are described in detail using the attached drawings, starting from a
system and method known from the prior art for CT-assisted imaging
monitoring of minimally-invasive interventions.

[0041]Various image acquisition methods and systems that are used for
visualization of internal organs, tissue regions, lesions or pathological
structures of a patient that are to be punctured are known from the prior
art. One of these systems is described in the medical professional
article "Intermittent-Mode CT Fluoroscopy-guided Biopsy of the Lung or
Upper Abdomen with Breath-hold Monitoring and Feedback: System
Development and Feasibility", (Radiological Society of North America,
RSNA, Oak Brook/Ill., December 2003, Vol. 229, Nr. 3, p. 906-912) by Dr.
Stephanie K. Carlson et al. This is a CT-based image acquisition system
with integrated respiration monitoring and display system MDS (called a
"Respiratory Bellows System") which was developed in the Department for
Radiology of the Mayo Clinic in Rochester (Minn.) and is used for
monitoring and optical feedback of the constancy of the inspiratory or,
respectively, expiratory pulmonary pressure (and therefore the breath
volume) given a breath-hold of a patient to be examined by means of CT
fluoroscopy. Among other things, this system has a pneumograph PG which
includes a respiratory belt AG expandable in the form of an air-filled
rubber bellows, which respiratory belt AG is wrapped around the upper
abdomen or, respectively, around the lower chest region of the patient.
The respiratory belt AG is thereby connected via an air-filled rubber
tube with a pressure-sensitive, piezoresistive, capacitive or inductive
transducer Td with which length changes of the belt (which correspond to
the circumference or, respectively, volume changes of the abdomen in the
inspiration or, respectively, expiration process, and thus changes of the
pulmonary pressure pM in the respiratory process) are detected in
the form of changes of the air pressure inside the rubber tube GS and are
converted into an electrical analog signal, for example into an analog
measurement voltage UM directly proportional to the detected
pulmonary pressure pM. The measurement signal can be modulated on a
radio-frequency analog carrier signal and, for example, be transmitted
wirelessly via a Bluetooth interface (including a radio wave transmitter
RFS1 and a radio wave receiver RFE1) to a first display unit
AE1. This display unit serves to indicate the signal amplitude of
the measurement signal corresponding to the respective respiration state
(i.e. the current position within the respiratory cycle) of the patient
by illuminating a corresponding number of light-emitting diodes of a
light-emitting diode row LZ1 to the left and right of a
light-emitting diode LEDM in the center of this light-emitting diode
row LZ1, which light-emitting diode LEDM emits light of a
different color. The patient is thereby instructed by a radiologist
implementing the examination to hold his or her breath and to inhale or
exhale only on command. Only the middle light-emitting diode LEDM of
the light-emitting diode row LZ1 then illuminates during an
inspiratory or, respectively, expiratory breath hold. Since the
aforementioned first display unit AE1 is advantageously
ergonomically mounted on a support arm TA permanently connected with the
patient table PT of a computed tomography scanner CTG and thus can easily
be viewed by a patient lying on the patient table PT, the patient has the
possibility to monitor the constancy of the breathing himself. The
radiologist can continuously track the time curve of the pulmonary
pressure on a further light-emitting diode row LZ2 of a second
display unit AE2 (likewise connected with the radio wave receive
RFE1) which is mounted above a display screen AB serving for
graphical visualization of interesting sub-regions of a tissue region or
organ to be presented by means of CT-assisted imaging and displays the
same signal as the light-emitting diode row LZ1 of the first display
unit AE1 that is visible by the patient, and if applicable said
radiologist can given further commands to inhale, exhale and/or hold
breath dependent on said time curve.

[0042]The respiratory monitoring and display system MDS described in the
preceding can thereby be controlled with the aid of a calibration and
control unit KSE. This calibration and control unit KSE in particular
serves to adjust a pressure reference value pM0 (desired value) to
which the deviations of the inspiratory or expiratory pulmonary pressure
(shown by the light-emitting diode rows LZ1 or LZ2 of the two
display units AE1 and AE2) should be related immediately before
and during a CT scan process. The establishment of this pressure
reference value can thereby ensue by momentarily throwing a switch KS at
a specific value of the pulmonary pressure pM or by inputting a
specific pressure value via a programmer or, respectively, data input
interface (not shown).

[0043]The calibration and control unit KSE can be connected to a further
radio wave transmitter RFS2 with which an analog voltage signal
UM0 proportional to a predeterminable desired value pM0 of the
pulmonary pressure pM is modulated on a radio-frequency analog
carrier signal and is transmitted (for example via Bluetooth) wirelessly
to the radio wave receiver RFE1 of the respiratory monitoring and
display system MDS described in the preceding. Moreover, the radiologist
has the possibility to suitably establish the beginning point in time
tSB or the end point in time tSE of a CT scan by the
calibration and control unit KSE and to wirelessly transmit a voltage
signal USB (corresponding to the beginning point in time tSB) and a
voltage signal USE (corresponding to the end point in time tSE)
to the central control device ZSE of the image processing system BVS (and
via this to the computed tomography scanner CTG) with the use of the
radio wave transmitter RFS2.

[0044]The RF signals sent from the respiratory monitoring and display
system MDS or from the calibration and control unit KSE can in turn be
wirelessly received (for example via Bluetooth) by a radio wave receiver
RFE2 connected with a measurement data input of the central control
device ZSE of the image processing system BVS via an analog-digital
converter ADU. Upon receipt by the central control device ZSE of the
image processing system BVS of the analog measurement signal UM, a
voltage signal USB establishing the beginning point in time tSB
and a voltage signal USE establishing the end point in time
tSE, the computer tomography apparatus CTG is instructed to
implement a CT scan process of the duration Δt=tSE-tSB.

[0045]Image data provided by the computed tomography apparatus CTG are
supplied to the image processing system BVS via an input/output interface
I/O. In addition to the central control device ZSE which controls the
data exchange with the computer tomography apparatus CTG as well as the
data exchange between the individual system components of the image
processing system BVS, the image processing system BVS can thereby
possess (among other things) suitable pre-processing filters as well as
software modules for segmentation and cluster formation (designated as a
pre-processing module VVM in the following) as well as an image rendering
module BRA for graphical visualization of segmented image regions in a
virtual object space in which sub-regions of the tissue region or organ
selectable by the radiologist are shown.

[0046]Upon receipt of image data from the computed tomography scanner CTG,
these can be stored either temporarily or persistently (depending on
system configuration) in an external image data storage in preparation
for a later graphical visualization. A copy of the image data is supplied
via the input/output interface I/O to the pre-processing module VVM
(cited in the preceding) which has a digital filter for noise
suppression, contrast improvement and edge detection. After filtering the
image data are registered by a segmentation and clustering module
(likewise contained in the pre-processing module VVM) and (if possible)
are merged ("clustered") into groups of similar or like image objects
arranged closely next to one another.

[0047]At the prompting of the central control device ZSE of the image
processing system BVS, the segmented and clustered image data are then
read out by an image rendering module BRA (which is required for
preparation of the image data for a two- and/or three-dimensional
graphical visualization) integrated into the image processing system BVS,
rendered and displayed on a display screen AB of a monitor terminal in
2D-rendered and/or 3D-rendered form in correlation with the inspiratory
or expiratory position within the respiratory cycle of the patient. For
the purpose of optical offsetting from the tissue surrounding them, the
individually segmented and clustered image regions can be emphasized via
different coloring. In this context both the generation of
maximum-intensity projections (MIPs) (method in which voxels of maximum
intensity are projected in an image plane, whereby a 3D impression of the
imaged tissue structures arises upon consideration from various viewing
angles) and a 3D post-processing (volume rendering) by means of
thin-slice multiplanar reformations (MPR) (wherein slice images in any
arbitrary slice plane are retroactively calculated from a volume data set
of a tissue region or organ to be examined that is acquired by means of
computer tomography) are possible.

[0048]The maximum contrast is achieved by an optimal coordination of the
contrast agent bolus injection with the image acquisition as well as via
an optimal bolus profile. In addition to what are known as "technical
pitfalls" that appear, for example, in the form of sub-volume effects and
contrast agent artifacts or, respectively, in the form of a weak
contrasting and are caused by an injection speed in the contrast agent
bolus injection that is too low, wrong bolus timing, or by a quantity of
contrast agent that is too small, respiration and pulsation artifacts
(what are called "patient-dependent pitfalls") in particular represent a
large problem in this context since these aliasing effects can have a
particularly disruptive effect in the framework of the image
interpretation. Namely, respiration artifacts can lead to abrupt contrast
variations and simulate intraluminal filling defects.

[0049]In order to generate optimally few movement artifacts, the image
data acquired by means of CT-assisted imaging are therefore typically
acquired in the framework of what is known as a continuous expiration CT
in the last phase of a forced expiration process. This technique is in
particular applied when patients, due to their reduced respiratory
reserve, are not in the position to hold their breath sufficiently long
enough after expiration in order to depict a tissue region to be examined
by means of computer tomography without overlap.

[0050]A block diagram of an image acquisition system according to an
exemplary embodiment of the present invention is shown in FIG. 1, which
image acquisition system serves for monitoring and display of the
pulmonary pressure as well as for CT-assisted imaging monitoring of a
minimally-invasive intervention at internal organs, tissue regions,
lesions or pathological structures of a patient to be punctured and is
similarly constructed in comparison to the conventional image acquisition
system explained in the preceding. The inventive image acquisition system
differs from the system illustrated above merely through the use of a
threshold decider downstream from the radio wave receiver RFE2 of
the image processing system BVS and realized as a window discriminator
FDk. This threshold decider delivers a binary output signal that,
assuming positive logic, only assumes the value "logical one" when the
measurement voltage UM reflecting the inspiratory or, respectively,
expiratory pulmonary pressure pM moves within a tolerance range
bounded by two suitably established thresholds UM,th1 and
UM,th2. The two cited thresholds UM,th1 and UM,th2 can
thereby be predetermined via a calibration and control unit KSE' and be
transferred wirelessly via the Bluetooth interface to the radio wave
receiver RFE2 of the image processing system BVS.

[0051]Via the discriminator circuit FDk (which is composed of two
comparator stages KP1 and KP2 connected at the output side with
the signal inputs of an AND-gate) it is thus ensured that the
aforementioned measurement data input of the central control device ZSE
is controlled in a value-discriminated manner. A first comparator stage
KP1 of the window discriminator FDk (which first comparator stage
KP1 is connected at the output with a first signal input of the
AND-gate G) that is charged by an inverted input with the measurement
voltage UM proportional to the detected pulmonary pressure pM
thereby serves for comparison of the amplitude values of this analog
signal with the voltage potential of a predeterminable upper threshold
voltage UM,th2 that is present at a non-inverted input of this first
comparator stage KP1. A second comparator stage KP2 of the
window discriminator FDk (the second comparator stage KP2 being
connected at the output with a second signal input of the AND-gate G)
that is charged via a non-inverted input with the measurement voltage
UM proportional to the detected pulmonary pressure pM serves
for comparison of the amplitude values of this analog signal with the
voltage potential of a predeterminable lower threshold voltage
UM,th1 that is present at an inverted input of this second
comparator stage KP2.

[0052]If the amplitude values of the analog measurement voltage UM
are in a value range below the voltage potential of the upper threshold
voltage UM,th2, the output voltage Uout1 of the first
comparator stage KP1 assumes the voltage potential of its positive
saturation voltage +USat which (assuming positive logic) corresponds
to a "high" level of Uout1. By contrast, if the amplitude values of
the aforementioned measurement voltage UM use in a value range above
the voltage potential of the upper threshold voltage UM,th2, the
output voltage Uout1 of the first comparator stage KP1 assumes
the voltage potential of its negative saturation voltage -USat which
(assuming positive logic) corresponds to a "low" level of Uout1.

[0053]In the second computer stage KP2 the relationships are
difference since the roles of both of the signals present at the
non-inverted or, respectively, inverted input of this comparator stage as
described in the preceding are swapped relative to those of the first
comparator stage KP1. If the amplitude values of the measurement
voltage UM lie within a value range above the voltage of the lower
threshold voltage UM,th1, the output voltage Uout2 of the
second comparator stage KP2 assumes the voltage potential of its
positive saturation voltage +USat which (assuming positive logic)
corresponds to a "high" level of Uout2. By contrast, if the
amplitude values of the aforementioned measurement voltage UM are in
a value range below the voltage potential of the lower threshold voltage
UM,th1, the output voltage Uout2 of the first comparator stage
KP2 assumes the voltage potential of its negative saturation voltage
-USat which (assuming positive logic) corresponds to a "low" level
of Uout2.

[0054]Since a binary signal with "high" level is provided via the output
of the aforementioned AND-gate G only when both input signals of this
AND-gate (i.e. the two digital output voltages Uout1 or,
respectively, Uout2 of the comparator stages KP1 and KP2)
respectively direct "high" levels, a binary signal commanding the
initiation of a CT scan process is only relayed to the central control
device ZSE of the image processing system BVS when the amplitude values
of the analog measurement voltage UM proportional to the detected
pulmonary pressure pM fall in terms of magnitude into the tolerance
range bounded by the two threshold voltages UM,th1 and UM,th2
of the window discriminator FDk; the inequality chain
UM,th1<UM<UM,th2 is thus satisfied. Compliance with
this condition is indicated by illumination of a light-emitting diode
LEDM emitting green light, which light-emitting diode LEDM is
arranged in the middle of the light-emitting diode row LZ1 or
LZ2 of the two aforementioned display units AE1 and AE2.

[0055]Given non-compliance with the aforementioned condition, the
magnitude of deviation between the analog measurement voltage UM and
a voltage level UM0 predeterminable by the radiologist and
proportional to a suitably established desired value pM0 of the
measured pulmonary pressure pM can be indicated (S4') via a light
signal emitted by two spatially separated display units AE1 and
AE2. The light signal is thereby formed via illumination of a number
(corresponding to the respective magnitude of deviation) of
light-emitting diodes emitting red light to the left and right of the
light-emitting diode LEDM emitting in the green spectral range in
the middle of the two light-emitting diode rows LZ1 and LZ2 of
these display units AE1 and AE2. The two display units AE1
and AE2 are arranged in an ergonomically advantageous manner so that
the display unit AE1 is easily visible by the patient to be examined
and the display unit AE2 by the radiologist.

[0056]At the end of the CT scan the signal values of UM are recorded
in a report file after translation into the corresponding pulmonary
pressure values, which report file is stored in a memory module of a
memory unit (not shown). According to the invention, between two CT scans
in immediate succession, the two preset thresholds UM,th1 and
UM,th2 can be automatically, respectively reset by the central
control device ZSE of the image processing system BVS or by the
calibration and control unit KSE' dependent on the stored signal values
of UM in order to adapt the size of the tolerance range to the
position of the patient within the respiratory cycle. At the end of a CT
scan a calibration signal can optionally also be transmitted from the
central control device ZSE of the image processing system BVS or from the
calibration and control unit KSE' to the inventive respiratory monitoring
and display system MDS', with which calibration signal the desired
voltage potential UM0 of the measurement voltage UM
proportional to the predeterminable desired value pM0 of the
pulmonary pressure pM is automatically reestablished. In this manner
it is ensured that the image data acquired in a CT scan process are
correlated with the displays of the two display units AE1 and
AE2 and consequently with the current position of the patient within
the respiratory cycle.

[0057]FIG. 2 shows a diagram reflecting the characteristic line curve of
the inspiratory or expiratory pulmonary pressure pM (in cmH2O)
over time t (in s) during a respiration period of duration
Δt.sub.AP,i of a patient, with which diagram it is illustrated how
the beginning point in time tSB and the duration Δt of a CT
scan to be implemented are determined according to the present invention.
As is apparent from the diagram, the phase of a CT scan lasts precisely
as long as the pulmonary pressure pM of the appertaining patient
moves around a desired value pM0 (not shown) within a tolerance
range bounded by two predeterminable pressure thresholds pM,th1 and
pM,th2, i.e. as long as the inequality chain
pM,th1<pM,EAH<pM,th2 is satisfied for a set constant
pulmonary pressure value pM,EAH given a breath hold conducted on
command. As shown in FIG. 3, given an expiratory breath hold that point
in time at which the characteristic breath hold curve falling
monotonically in the range of the expiration phase has dropped to the
value pM,th2 (i.e., to the upper of the two pressure thresholds)
consequently arises as a beginning point in time tSB of the CT scan.
Conversely, given an inspiratory breath hold that point in time at which
the characteristic breath hold curve rising monotonically in the range of
the inspiration phase has risen to the value pM,th1 (i.e., to the
lower of the two pressure thresholds) arises as a beginning point in time
tSB of the CT scan. In both cases the end point in time tSE is
that point in time at which the patient resumes breathing again; as a
result of an inhalation or exhalation, the pulmonary pressure is thus set
to a value outside of the tolerance range bounded by the two pressure
thresholds pM,th1 and pM,th2. According to this exemplary
embodiment of the present invention, beginning point in time tSB and
end point in time tSE of a CT scan to be implemented are thus
determined dependent on the acquired characteristic pulmonary pressure
curve, meaning that a CT scan is inventively automatically initiated or,
respectively, ended dependent on the determined values of tSB and
tSE.

[0058]FIG. 4 is a flowchart illustrating a conventional method for
CT-assisted imaging monitoring of a minimally-invasive procedure
implemented after local anesthesia at punctured internal organs, tissue
regions, lesions or pathological structures of a patient. After
measurement (S1a) of the pulmonary pressure pM by detection of
circumference or volume changes of the abdomen in an inspiration or
expiration event of the patient to be treated and conversion (S1b) of the
detected measurement signal into an electrical analog signal (for example
into an analog measurement voltage UM), the patient is instructed to
hold his breath (S2) through a command of a radiologist conducting the
examination. When the measured pulmonary pressure pM has adjusted to
a constant value, the radiologist manually initiates a CT scan (S3a) in
order to acquire image data of axial, sagittal and/or coronal
cross-section depictions (in the form of greyscale images of a specific
resolution) of regions of interest of the internal organs, tissue
regions, lesions or pathological structures of this patient that are to
be punctured. The magnitude of deviation between the analog measurement
voltage UM and a desired value UM0 predetermined by the
radiologist is thereby indicated by a light signal (S3b) at two spatially
separate display units AE1 and AE2 both before and during the
CT scan, which display units AE1 and AE2 are arranged such that
the display unit AE1 is easily visible by the patient and the
display unit AE2 by the radiologist. The image data acquired by
means of computed tomography are subsequently imported into an image
processing system BVS (S4a) and an optional pre-processing filtering
(S4b) for noise suppression, contrast improvement and edge detection of
these image data is implemented. The filtered image data are subsequently
subjected to a segmentation and clustering algorithm (S4c) before the
characteristic line curve of the measured pulmonary pressure pM over
time t and the image data rendered with the aid of a 2D/3D image
rendering application BRA into 2D slice images or 3D reconstructions are
visualized on a display screen AB of a monitor terminal in graphical form
(S4d).

[0059]FIG. 5 is a flowchart of an embodiment of the inventive method for
correlating CT-assisted imaging monitoring of minimally-invasive
procedures at internal organs, tissue regions, lesions or pathological
structures of a patient that are to be punctured, with the inspiratory or
expiratory position of the patient within the respiratory cycle. The
method, which is implemented using the image acquisition system shown in
FIG. 1, begins with the patient being requested by a radiologist
conducting the examination to hold his or her breath or to breathe as
slowly as possible (S1'). The pulmonary pressure pM of the patient
is thereupon measured in that circumference or volume changes of the
abdomen are detected (S2a') in the inspiration or expiration process as
well as in the phase of the breath hold and the acquired measurement
signal is converted (S2b') by means of a pressure-sensitive transducer Td
into an electrical analog signal, for example into an analog measurement
voltage UM proportional to pM. In a step S3' it is queried
whether the voltage potential of the measurement voltage UM relative
to ground lies within a value range ]UM,th1, UM,th2[
predeterminable by the radiologist. If this is not the case, the
magnitude of deviation between the analog measurement voltage UM and
a desired value UM0 (likewise predeterminable by the radiologist) is
indicated (S4') via a light signal on two spatially separate display
units AE1 and AE2. The latter are arranged such that the
display unit AE1 is easily visible by the patient to be examined and
the display unit AE2 by the radiologist. The measurement of the
pulmonary pressure pM is continued during this time, meaning that
the method begins anew with step S2a'. Otherwise a CT scan is
automatically initiated (S5') by the central control device ZSE of the
image processing system BVS in order to acquire image data of axial,
sagittal and/or coronal cross-section depictions (in the form of
greyscale images of a specific resolution) of regions of interest of the
internal organs, tissue regions, lesions or pathological structures of
this patient that are to be punctured. The pulmonary pressure pM is
thereby continuously measured via detection of circumference or volume
changes of the abdomen in an inspiration or expiration event as well as
in the phase of the breath hold (S6a'), and the acquired measurement
signal is converted (S6b') into an electrical analog signal, wherein this
is in turn an analog measurement voltage UM proportional to pM.
In a step S7' it is then in turn queried whether the voltage potential of
the measurement voltage UM relative to ground is within a value
range ]UM,th1, UM,th2[. If this is the case, the CT-supported
imaging process for acquisition of image data of axial, sagittal and/or
coronal cross-section depictions is continued (S8') and the method begins
anew with step S6a'. If, by contrast, the voltage potential of the
measurement voltage Um lies within the aforementioned value range, the
image data acquired by means of computer tomography are imported (S9')
into the image processing system BVS. After an optional pre-processing
filtering for noise suppression, contrast improvement and edge detection
of the acquired image data (S10a'), the filtered image data are subjected
to a segmentation and clustering algorithm (S10b'). The method ends with
the characteristic line curve of the measured pulmonary pressure pM
over time t and the image data, rendered with a 2D/3D image rendering
application BRA into 2D slice images or 3D reconstructions, being
presented on a display screen AB of a monitor terminal in graphical form
(S11').

[0060]Before, during, and after conclusion of the CT scan, the radiologist
has the possibility to have the time curve of the inspiratory or,
respectively, expiratory pulmonary pressure pM (detected by the
respiratory monitoring and display system MDS and indicated by the in the
form of a time-variable light signal emitted by light-emitting diodes of
the display unit AE2) displayed in the form of a characteristic
pulmonary pressure curve pM(t) on the display screen AB of the
monitor terminal. In this manner the radiologist is placed in the
position to assess whether the current position of the patient within the
respiratory cycle (i.e. the value of the inspiratory or, respectively,
expiratory pulmonary pressure pM at a monitoring point of time
tSE at the end of a CT scan) corresponds to the position within the
respiratory cycle during the duration Δt of an implemented CT scan
or is within a tolerance range around the predetermined desired value
pM0, which tolerance range is bounded by the thresholds pM,th1
and pM,th2. If this is the case, work can proceed safely, which is
of great importance in a CT-controlled minimally-invasive procedure, for
example given the extraction of a tissue sample (biopsy); if this is not
the case, corresponding commands to inhale, exhale or hold the breath
further can be given to the patient. Moreover, the patient has the
possibility to monitor his or her position within the respiratory cycle
himself by tracking the display on the display unit AE1 and regulate
based on the desired value pM0 or, respectively, on a pulmonary
pressure value lying within the value range between pM,th1 and
pM,th2. The radiologist can thus be sure that the spatial position
and anatomical shape of a sub-region (shown on the display screen AB as a
2D or 2D raster graphic) of the tissue region or organ that is to be
examined coincides with the position and shape of this sub-region that is
actually dependent on the current position of the patient within the
respiratory cycle. Puncture targets (for example in the region of the
liver, in the region of the upper abdomen or in the region of the lung)
provided for a tissue extraction and dependent on the current position
within the respiratory cycle can thus be percutaneously punctured with
the aid of a puncture needle. An advantage of the method according to the
invention relative to the prior art is thus that puncture errors, which
are ascribed to a variation of the respiratory cycle position of a
patient to be examined under CT-assisted imaging monitoring that goes
unnoticed by the radiologist, can be avoided.

[0061]Although modifications and changes may be suggested by those skilled
in the art, it is the intention of the inventors to embody within the
patent warranted hereon all changes and modifications as reasonably and
properly come within the scope of their contribution to the art.